Method for recovering vanadium from iron-base alloys



3,460,937 METHOD FOR RECOVERING VANADIUM FROM IRON-BASE ALLOYS Heinrich W. Rathmann, Cambridge, Ohio, assignor to Foote Mineral Company, Exton, Pa., a corporation of Pennsylvania No Drawing. Filed Aug. 31, 1967, Ser. No. 664,619

Int. Cl. C221) 55/00, 7/00 US. C]. 75-84 10 Claims ABSTRACT OF THE DISCLOSURE A method for extracting vanadium from any iron-base alloys, for example, ferrophosphorus, by heating a molten iron-base allow containing vanadium with an oxide having a low heat of formation and silica to form .a molten alloy and slag containing the vanadium as an oxide which may be separated from the molten alloy and treated to extract the vanadium.

My invention relates to the removal of vanadium from iron-base alloys and specifically from ferrophosphorus by the preferential oxidation of vanadium from ferrophosphorus to produce a slag having an improved vanadium/ phosphorus ratio.

Ferrophosphorus is a by-product obtained during electric furnace smelting of phosphate rock in the production of elemental phosphorus. In this process the elemental phosphorus is volatilized and the iron present in the phosphate rock forms ferrophosphorus, the quantity of which increases with the iron content of the charge. The phosphate rock from which the ferrophosphorus is made contains approximately 0.1% to 0.50% V By-product ferrophosphorus contains about 24% to 28% phosphorus, 3.5% to 8% vanadium, and the balance iron and minor amounts of other elements present in the phosphate rock. This constitutes a substantial source of vanadium.

Various methods have been proposed for the removal of vanadium from ferrophosphorus including blowing the ferrophosphorus with oxygen. Oxygen blowing has the advantage of removing most of the vanadium, but the disadvantage of removing phosphorus and other elements present. The oxides form a slag containing a high percentage of P 0 My invention, on the other hand, provides a novel and economical process for preferentially removing vanadium from ferrophosphorus in a siliceous slag. I have found that the addition of silica to the slag suppresses the oxidation of phosphorus while increasing the oxidation of vanadium. The slag produced in accordance with my invention has a vanadium/phosphorus ratio substantially higher than ferrophosphorus or slags produced by oxidation of ferrophosphorus without the addition of flux.

Generally, my method includes mixing together ferrophosphorus, an oxide having a low heat of formation such as iron oxide and an acid slag former such .as silica and charging said mixture in an electric furnace. As the charge melts, the vanadium is preferentially oxidized and combined with the silica to form a slag. After the charge is completely molten .and the reactions completed, the molten alloy and slag are poured into a mold and separated. The slag may then be prepared for further treatment by well-known methods to extract the vanadium.

'United States Patent 0 F. to 1600 F., thereby converting the vanadium to water soluble sodium vanadate and then leaching the roasted residue with water to extract the vanadium.

My novel method can be used to remove vanadium from any iron-base alloy such as a vanadieferous pig iron. However, it is particularly adapted to iron-base .alloys containing an acid element such as phosphorus which is not desired in the slag from which the vanadium is to be subsequently removed.

Any oxide having a heat of formation lower than V 0 may be used. Thus, for example, iron oxide, copper oxide, and nickel oxide may be used. I prefer to use iron oxide, particularly hematite ore (Fe O because it contains more oxygen per unit weight of iron. However, mill scale or magnetite ore (Fe O are very satisfactory.

Any acid slag former may be used and will suppress the oxidation of acid elements such as phosphorus. Silica is preferred; however, titanium oxide, boric oxide, etc. may be used, but tend to be less effective or too expensive.

In Table I below I have set forth the broad and preferred ranges of the charge added to an electric furnace in carrying out my invention:

TABLE I Broad range Preferred range Charge (percent) (percent) Ferrophosphorus -80 -70 Iron oxi 10-50 15-25 Silica 10-30 15-20 A low percentage of iron oxide will oxidize only a small phorus oxidation, while a high percentage will dilute the vanadium content of the slag. Accordingly, an addition of 18% silica seems to offer the best balance of these factors.

Any temperature at which the alloy and the slag are fluid is satisfactory. The temperature range in which the charge is satisfactorily melted is between 2860 F. to 3360 F. However, I prefer that the temperature be maintained below 3200 F. to avoid undue refractory attack, accordingly, the preferred range is between 2860 F. and 3200 F.

The following nonlimiting examples further illustrate my invention.

Example I The following mixture was charged in an electric arc furnace:

Lbs. Ferrophosphorus 200 Mill scale 60 Silica sand 58 The ferrophosphorus had the following constituents:

Percent Vanadium 7.59 Phosphorus 26.40 Chromium 5.75 Nickel 1.44 Silicon 0.80 Carbon 0.067 Iron Balance and the vanadium/ phosphorus ratio was 0.29.

After the mixture became molten, a slag sample was taken. In normal production the slag and metal would have been separated and the vanadium removed from the slag by known methods. However, in order to further explore the reaction, three successive additions of 40 very high vanadium/ phosphorus ratio as illustrated by the initial melt in Example I. To remove most of the vanadium in a one step process, additional quantities of iron oxide may be added as in the examples and a slag having a moderately high vanadium/ phosphorus ratio as is ilpounds each of mill scale were made to oxidize additional 5 lustrated by the final slag in Example I. vanadium. After each addition had become molten, slag As a two step operation, a slag having a very high vanasamples were taken. The analysis of the slag samples is dium/ phosphorus ratio as illustrated by the initial melt shown in Table II. in Example I is prepared in the first step. Approximately TABLE II V205 P205 SiOz FeO (percent) (percent) (percent) (percent) V/P ratio Initial melt 12.82 4. 37 44. 76 11. 23 3. 76 After first additio 9. s2 4. 37 31. 72 26. 50 2. 88 After second addition 7. 82 4. 37 26. 96 28. 22 2. 29 After third addition 7.10 5. 52 25.12 27. 65 1.67

The slag also contained minor amounts of chromium one half of the vanadium content of the ferrophosphorus and nickel oxides and some contamination from the is removed in this step. The slag is separated from the furnace lining. The final slag weighed 272 pounds and conmolten alloy and new additions of iron oxide and silica tained 72.2% of the vanadium but only 12.4% of the are made to the furnace containing the molten alloy. Alphosphorus of the original ferrophosphorus. After the most all of the vanadium remaining in the ferrophos reaction was completed, the metal and alloy were tapped phorus is recovered in the second step which produces a into a cast iron mold. Slag with a relatively low vanadium content and vana- The refined ferrophosphorus weighed 207 pounds and dium/ phosphorus ratio. This slag may then be used on contained in addition to iron and impurities a new quantity of ferrophosphorus. By recycling the slag Percent to the first step of a new cycle, advantage may be taken Vanadium 0.94 of the high iron oxide content of the slag and the overall Phosphorus 19.00 twc; step operation gives a vanadium recovery exceeding 30 90 o. Wlth a Vanadlum/Phosphorus who of While I have described certain presently preferred em- Exarnple II bodiments of my invention, it may be otherwise em- The following mixture was charged in an electric arc bodled ,wlthm the Scope of th appended claimsfurnace in the same manner as in Example I: I 01mm:

Lbs. 1. A method for removing vanadium from an iron-base Ferrophosphorus 179 alloy 1 Min scale 60 (A) mixing an iron-base alloy containing between Silica sand 58 and 80 wt. percent of vanadium, between 10 and 30 wt. percent of an acid slag former and between 10 ferrophosphorus thls example had P 40 and 50 wt. percent of an oxide having a heat of viously been partially oxidized to remove 51% of the formation lower than V205 to form acharge; vanadium. The ferrophosphorus had the following con- 1 melting Said charge to cause f ti of an acid Stltlltentsi slag containing an oxide of vanadium; and

Percent (C) separating the slag containing the vanadium from Vanadlum said iron-base alloy. Phosphorus 24-00 2. A method as set foith in claim 1 wherein Said iro and the vanadium/ phosphorus ratio was 0.17. base alloy is ferrophosphorus- Aft h mixture became molten, a Slag sample was 3. A method as set forth in claim 1 wherein said oxide taken. Thereafter, two successive additions of 40 pounds is an iron OXideeach of mill scale were made to oxidize additional vanadi- A method s et f rth in claim 1 wherein said acid um. After each addition had become molten, slag samples slag former is silica, were taken. The analysis of the slag samples is shown in 5. A method for removing vanadium from ferro- Table III. phosphorus comprising:

TABLE III V205 P205 sior FeO (percent) (percent) (percent) (percent) V/P ratio Initial innit 4. 91 6. 41 40. 52 28. 22 0. 98 After first addition... 4. 91 5. 90 a2. 40 40. 03 1.07 After second addition 5.18 10.30 27.68 37. 44 0. 64

The ferrophosphorus weighed 185 pounds and contained (A) forming a charge containing between 40 and in addition to iron and small percentages of chromium, 80 wt. percent of said ferrophosphorus, between 10 Ilifikel, Silicon and Carbon, and 50 wt. percent iron oxide, and between 10 and Percent 30 wt. percent silica; Vanadlllm 5 (B) melting said charge to cause formation of a Phosphorus 0 siliceous slag containing an oxide of vanadium; a d and the vanadium/phosphorus ratio was (C) separating said slag containing the vanadium from The slag contained 73.2% of the inbound vanadium and Sald ferrophosphorus to thereby remove the vanadium 19.4% of the inbound phosphorus, while the final ferrofrom the ferrophosphorflsphosphorus contained only 71% of the inbound Vana 7 6. A method as set forth in claim 5 wherein the charge dium.

The process may be operated either as a one step process as described above or as a two step process. As a one step operation approximately one half of the vanadium can comprises between 50 and wt. percent ferrophosphorus, between 15 and 25 wt. percent iron oxide, and between 15 and 20 wt. percent silica.

7. A method as set forth in claim 5 wherein after the be extracted from the ferrophosphorus as a slag having a 75 original charge is molten an additional quantity of iron 5, oxide is added to the molten charge and is melted prior to separation of the slag from the ferrophosphorus.

8. A method for removing vanadium from ferrophosphorus comprising:

(A) forming a charge containing between 40 and 80 Wt. percent of said ferrophosphorus, between 10 and 50 wt. percent iron oxide, and between 10 and 30 wt. percent silica;

(B) melting said charge to cause formation of siliceous slag containing an oxide of vanadium;

(C) separating said slag from said ferrophosphorus thereby removing some of the vanadium from the ferrophosphorus;

(D) adding an additional quantity of iron oxide and silica to the molten ferrophosphorus derived from step C;

(E) melting the new charge to form a new step B; and.

(F) separating the second siliceous slag containing additional vanadium values from the ferrophosphorus to thereby remove additional vanadium from said ferrophosphorus.

9. A method as set forth in claim 8 including the following steps:

(A) mixing the siliceous slag obtained in step F with ferrophosphorus, iron oxide and silica to form a third charge;

(B) melting the third charge to cause formation of additional siliceous slag containing vanadium;

(C) separating the slag containing vanadium from the ferrophosphorus.

10. A method as set forth in claim 9 wherein the ferrophosphorus obtained in step C is subsequently melted with additional iron oxide and silica to form a siliceous slag containing additional vanadium.

References Cited UNITED STATES PATENTS 2,467,039 4/ 1949 Kersch'baum et a1. 75-84 X 2,654,655 10/1953 Banning et al. 75132 X 3,154,410 10/1964 Darrow et a1 7584 X 3,305,355 2/1967 Darrow et al 75132 CARL D. QUARFORTH, Primary Examiner M. J. SCOLNICK, Assistant Examiner US. Cl. X.R. 

